Cutting down the Q-biotype whitefly

Whitefly

Cutting down the Q-biotype whitefly

A national task force and its allies are leading the fight against Bemisia tabaci.

Patrick Williams

Adult Bemisiatabaci

Photo courtesy of Dr. Lance Osborne

Although they are ultimately dealing with the same species, it behooves entomologists to separately monitor Bemisia tabaci Q-biotype populations from those of the B-biotype, and they are doing just that. The Q-biotype, which was discovered after the B-biotype, is more resistant to insecticides. In 2004, it caused alarm among specialty and commodity crop producers. Years after populations shrunk, they returned with a vengeance. Now, they may be declining again.

“Every year, the Q comes in on, to be honest, ornamental cuttings, and spreads around the country, but we’ve been able to prevent it from getting out of greenhouses,” says Dr. Lance Osborne, professor of entomology at the University of Florida.

That is, until 2016, when Q-biotype populations were discovered in West Palm Beach, Fla. It is because of this discovery, Osborne says, that a group in which he is involved, revamped its efforts to fight the Q-biotype and prevent it from getting loose into commodity crops.

The Whitefly Q-biotype Task Force was originally organized in 2004 by the New Pest Advisory Group (NPAG), which was convened by the United States Department of Agriculture - Animal Plant Health Inspection Service - Plant Protection Quarantine (USDA APHIS-PPQ). Osama El-Lissy, deputy administrator of PPQ, chaired the task force, which was divided into three groups: a regulatory group consisting of state and federal government regulators, an industry group consisting of crop producers, and a scientific group.

“We’re not just trying to manage the Q whitefly,” Osborne says. “We’re trying to manage resistance in the B-biotype as well, because a B-biotype could be more problematic than a Q. It seems to have greater fecundity [lays more eggs].”

In areas where scientists have tried to keep a colony of Q-biotypes, and B-biotypes have entered, the colonies eventually turned into full colonies of B-biotypes. “They’re more aggressive, so we don’t want B, either,” Osborne says.

A close-up of Bemisia tabaci on hibiscus

Photo courtesy of Dr. Lance Osborne

From B to Q

Before the establishment of the task force, swarms of B-biotype whiteflies resembling clouds decimated crops in the Southwestern United States. “People driving through the desert southwest would have to pull over and wash their windshields because there were so many whiteflies stuck to them,” Osborne says.

Scientists from the area had developed a management program to prevent whitefly outbreaks and manage resistance to the pests. The group was led by Dr. Timothy Dennehy, who then worked as a professor at the University of Arizona. He collected whiteflies from a retail outlet that was selling poinsettias in December and took them to a lab to test them for resistance.

“The lab techs said, ‘This colony is from a different world because there’s nothing that’s killing them. They are very, very resistant to the compounds that they are using,’” Osborne says. “That was when the whitefly was analyzed biochemically, and it was found to be the Q.”

Scientists discovered the wholesale supplier of the plant material was in California. Arizona quarantined ornamental plants from coming into the state because of the Q-biotype, and panic ensued.

Creating a management plan

The Whitefly Q-Biotype Task Force was organized to prevent trade restrictions, and it allayed fears, Osborne says. It developed a system for tracking the Q-biotype that relied on anonymous submissions of whitefly. “You could send samples in to one of three labs,” he says. “The report would just go by what state Q was found in, and no details of the grower, the county, or anything like that. It allowed us to track and show that it was still moving, and it was found in some 20-plus states.”

Bemisia tabaci on hibiscus

Photos courtesy of Dr. Lance Osborne

Additionally, scientists developed a whitefly management plan with experts such as Dr. Cindy McKenzie of USDA ARS Florida, James A. Bethke of the University of California Cooperative Extension and Dan Gilrein of Cornell University. They put together what Osborne calls “a best-guess scenario” of how to manage the Q-biotype that could also be used for the B-biotype. “That’s been the basis for managing whiteflies, in my estimation, ever since,” Osborne says. “That’s on a number of websites, and we’ve updated it almost every year. As soon as we get a new chemical available, we put it into the program.” None of this effort, Osborne, says, would have been possible without regulatory support from USDA APHIS and biotyping by McKenzie.

A winter with fewer whitefly

Osborne suspects the most recent flareup in Q-biotype populations resulted, in part, from warmer winters and growers not sticking to their insecticide rotations. Whitefly are known to be a nuisance on poinsettia, but they have affected numerous ornamentals, including, notably, hibiscus. The good news, Osborne says, is that in the winter of 2017-2018, he hasn’t received as many phone calls about whitefly on poinsettia as he has in previous years.

With the help of APHIS, AmericanHort, the Society of American Florists (SAF) and the Florida Nursery, Growers and Landscape Association (FNGLA), entomologists have discovered four insecticides that are effective on the Q-Biotype. “Growers should participate and support these organizations because they go to the federal government and other states to make sure that trade isn’t closed down,” Osborne says. “If we do the right thing, we can continue to go and do business as usual.”